The known extracorporeal blood treatment apparatus comprise at least a treatment unit (for example a dialyser or filter or an ultrafilter or a plasma filter or a filter unit of a different type) having a semi-permeable membrane which separates the treatment unit into two chambers. An extracorporeal blood circuit enables circulation of blood taken from a patient within the first chamber. At the same time, and typically in a counter-current direction with respect to the blood, a treatment fluid is circulated across a special circuit in the second chamber of the treatment unit. A blood removal line is connected with an inlet port of the first chamber and is predisposed, in operating conditions of connection to a patient, to remove blood from a vascular access inserted, for example, in a fistula on the patient. A blood return line connected with an outlet port of the first chamber is predisposed to receive the blood treated by the treatment unit and to return the treated blood to a further vascular access connected to the patient's fistula. A peristaltic pump operatively coupled to the extracorporeal blood circuit circulates the blood in the circuit. This type of blood treatment apparatus, known as dialysis apparatus, can be used for removal of solutes and excess fluid from the patient's blood where the patient is suffering from kidney failure.
During this treatment it is necessary to monitor and analyse the behaviour of the patient's physiological pressure generators, such as the heart and/or the breathing system. For example, to monitor the heartbeat of a subject, the blood pressure and also the state of the vascular accesses (for example to identify the dislodgement of the venous needle VND), it is advisable to extract/isolate the pressure data deriving from the physiological pressure generators. To this end the pressure signals detected by special sensors arranged in the extracorporeal blood circuit must be treated/filtered in order to remove noise.
The Applicant has observed that the existing and known solutions operating the treatment/filtering operations require large memory capacity and computational power in order to process the pressure signals in the most efficient way with the aim of guaranteeing the correct functioning of the apparatus and the respect of the treatment parameters of the patient.
In particular, the Applicant has observed that the performance of the algorithms at the base of the treatment of pressure signals is negatively influenced by the fact that the sampling frequency of the pressure signals is constant so that the samples acquired in a rotation of the pump decrease as the rotation velocity of the pump increases, and vice versa.